Bipolar Ventricular Tachycardia (VT) Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Bipolar Ventricular Tachycardia (VT) Study (NCT02374476), a non-randomized na study. The primary outcome is Number of Participants Achieving Freedom From Recurrent Ventricular Tachycardia (VT).

2. Clinical Question

The clinical question in the registry is whether bipolar radiofrequency ablation can be used in the setting of refractory VT after standard unipolar ablation has been unsuccessful, and what safety and outcome information is observed. Its stated hypothesis is that greater current density and improved transmural lesion creation could lead to arrhythmia termination with minimal or no increased risk of complication. That statement is a hypothesis, not a reported finding.

The record’s stated rationale describes bipolar energy as traveling between two catheter tips on opposite sides of the heart muscle, in contrast with unipolar energy traveling from a catheter tip to a grounding pad. The primary endpoint focuses on recurrent VT at a specified follow-up time rather than only the immediate procedural outcome. However, the endpoint count and any estimate of uncertainty are not reported in the registry record, so the posted information does not answer how often freedom from recurrence was achieved.

3. Trial Design

This was a completed, non-randomized, parallel-model study of bipolar ablation for refractory scar-related ventricular arrhythmia. The registry lists no masking and phase as NA. Enrollment is listed as 145. The registry lists a start date of 2015-02-18 and a primary completion date of 2020-04-01. These details describe the study record; they do not establish the number of participants included in each outcome analysis.

The intervention was bipolar ablation. The record describes the intended intervention group as participants who met inclusion criteria and had VT not terminable with unipolar ablation. The registry group comprised participants after standard unipolar radiofrequency ablation was successful. The groups therefore reflect different clinical pathways rather than allocation to alternative procedures under a randomized scheme. The registry itself cautions that the arms are not a like-for-like control comparison.

That design distinction matters when reading outcome differences. The reasons participants received one pathway rather than the other are tied to the success or failure of prior unipolar ablation. Random assignment, which can help balance known and unknown prognostic factors on average, was not used. Consequently, any differences in posted outcomes could reflect group composition or the preceding treatment experience as well as the procedures being described. The record does not report an adjustment strategy that would address those possible differences.

The record lists six outcome measures and zero analyses. It lists one primary outcome, freedom from recurrent VT at 6 months, and secondary outcomes concerning procedural complications, post-ablation inducibility, time to arrhythmia termination in the bipolar group, duration of bipolar ablation, and mortality. Outcome results beyond the posted adverse-event figures are not reported in the registry record. The protocol, detailed eligibility criteria, recruitment flow, and reasons for any exclusions are not reported in the registry record.

Although enrollment is listed as 145, the adverse-event figures use group denominators of 49 and 60. The record does not explain how those denominators relate to total enrollment or to the analysis population for the primary endpoint. They should not be treated as a complete accounting of enrollment without that explanation. The registry record also does not report the sample-size justification or whether any interim analyses were planned or conducted.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

VT Induced Ablation

Reasons for not completing this period:

Arm Assignment

Reasons for not completing this period:

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants Achieving Freedom From Recurrent Ventricular Tachycardia (VT), measured over 6 months.

The primary endpoint is the number of participants achieving freedom from recurrent ventricular tachycardia at 6 months. The registry defines recurrence as sustained VT lasting longer than 30 seconds, identified because of clinical symptoms or during device interrogation. It is a participant-count outcome: the intended result is a count of people meeting the endpoint definition, rather than a measurement of the duration or frequency of every episode.

A recurrence endpoint is used to describe whether the arrhythmia returned during the specified follow-up period. Setting a follow-up time gives the outcome a defined observation window, while a clinical or device-based identification rule states what qualifies as recurrence. These definitions are important because endpoint results depend on how an event is recognized and classified. The record’s definition includes both symptom-based identification and device interrogation.

The registry record does not report the number achieving freedom from recurrent VT, the number with recurrence, or an uncertainty estimate for the primary endpoint. It also does not report details such as the handling of participants who died, withdrew, or lacked complete follow-up before 6 months. Without those details and the endpoint result, the listed definition alone cannot establish the frequency of recurrence or the precision of any estimate.

Freedom from recurrence is distinct from immediate procedural termination, post-ablation inducibility, and procedural complications. Those are separate clinical or procedural outcomes in the registry’s outcome list. A result on one of them would not, by itself, supply the missing primary endpoint result or determine how recurrence was assessed through the full follow-up period.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What kind of outcome is the primary measure?

The primary measure is a count of participants meeting a binary endpoint definition: freedom from recurrent VT at 6 months. A binary endpoint classifies each participant into a defined outcome category, such as meeting or not meeting the stated criterion. The count is the number of participants in one category. To interpret such a count fully, readers also need the number of participants assessed and a clear account of how incomplete follow-up and other endpoint situations were handled. Those details and the primary endpoint result are not reported in the registry record.

A count is not itself a comparative treatment effect. A comparison generally requires both outcome information and a suitable analysis plan, with attention to the groups being compared and the uncertainty in the estimates. Here, the registry record describes a non-randomized comparison between participants whose VT was not terminable with unipolar ablation and a registry group following successful unipolar ablation. Because the pathways differ, an unadjusted difference would not automatically represent an effect attributable to bipolar ablation.

Why does the design affect interpretation?

In a randomized trial, treatment allocation is determined by chance. This can help make groups comparable in expectation, although it does not guarantee balance in every study. In this study allocation is listed as non-randomized. Participants’ treatment pathways were related to whether unipolar ablation was successful. That history may be relevant to subsequent outcomes, so the groups cannot be treated as interchangeable by default. The registry record does not report randomization, masking, or an adjustment plan that would support a causal comparison. Masking is listed as none.

General statistical principle: confounding occurs when factors associated with group membership are also related to an outcome. In a non-randomized comparison, observed outcome differences can combine treatment-related differences with differences in participant characteristics, clinical history, or care pathways. Statistical adjustment can sometimes address measured factors, but cannot guarantee removal of unmeasured confounding. No such adjustment results are reported in the registry record.

What does a confidence interval communicate?

General statistical principle: a confidence interval gives a range of values compatible with the data and the assumptions of the method used. It communicates precision as well as direction and magnitude; a wider interval indicates less precision. It does not mean that the true value has a specified probability of being inside that particular calculated interval. The registry record does not report a confidence interval for the primary endpoint or for a comparative treatment effect. Consequently, the precision of the primary outcome estimate cannot be evaluated from the posted record.

The lack of a reported interval is especially important when interpreting participant counts. A count without a clear denominator does not show how common an outcome was in the population of interest. A count with a denominator still does not, alone, describe uncertainty or establish a difference between treatment pathways. The adverse-event counts include denominators for the listed groups, but the record does not provide a statistical comparison or clarify all details needed to interpret the denominators and event categories.

How should adverse-event counts be read?

The registry lists participants at risk and participants affected for serious and other adverse-event categories, as well as deaths. These are descriptive safety data. A participant count is not necessarily a count of distinct event episodes: one person may experience more than one event, and the record does not explain whether the categories overlap. The listed top serious-event terms are accompanied by percentages, but denominators and group-specific interpretation for those percentages are not stated in the posted information.

General statistical principle: safety comparisons require attention to exposure, follow-up duration, event definitions, and whether the measure counts people or events. They also require consideration of the study design and uncertainty. A raw count can inform what was recorded, but it cannot establish that a procedure caused an event or show that one group had greater risk than another. The non-randomized design and the different treatment pathways further limit such comparisons in this study.

What is the role of the planning illustration?

The record describes sample-size assumptions for a planning illustration based on an observed effect, not on the trial’s own design. The stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. For time-to-event outcomes, the stated planning quantity is the total number of events; other outcomes use participants per arm.

Such sample-size calculations are planning illustrations, not observed power and not evidence that a study was adequately designed. They depend on assumptions about the effect to detect and the analysis. The registry record does not report the trial’s sample-size justification, and the primary endpoint result needed to understand any illustration based on the observed effect is not reported. The assumptions should not be mistaken for a description of the actual allocation or actual analysis.

The registry lists zero analyses. It does not report inferential results for the primary endpoint or a statistical analysis plan. There is therefore no basis in the registry record for reconstructing a formal model, determining whether estimates were adjusted, or assessing how uncertainty was calculated. Any method-specific interpretation beyond the listed design and planning assumptions would be speculation.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Bipolar Ablation", "Patient Registry")
n      <- c(49, 60)
events <- c(16, 29)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Bipolar Ablation  49  16  32.7  19.9  47.5  21.2  46.6  21.2  46.7
ARM  Patient Registry  60  29  48.3  35.2  61.6  36.2  60.7  36.1  60.7

11. Multiplicity, Missing Data and Analysis Populations

The registry lists six outcome measures, including the primary endpoint and secondary measures concerning procedural complications, post-ablation inducibility of VT, time to arrhythmia termination in the bipolar group, duration of bipolar ablation, and mortality. Considering several outcomes can create a multiplicity issue: when many hypotheses are tested, the chance of at least one apparently notable result can increase. General statistical practice may address this through a prespecified hierarchy, adjustment, or a clearly exploratory interpretation. The registry record does not report a multiplicity strategy.

The record lists zero analyses and does not provide results for the primary endpoint or most of the secondary outcomes. It does not report whether analyses were planned for each outcome, which outcomes were formally tested, or whether any method was used to control multiplicity. Without that information, no conclusion can be drawn about the statistical status of unreported outcomes or about selective reporting.

Missing-data handling is also not reported in the registry record. The primary endpoint is defined at 6 months, but the record does not state how participants without complete follow-up, participants with missing device data, or participants who died before assessment were handled in the endpoint analysis. It also does not report a missing-data assumption or sensitivity analysis. These details matter because an estimate can depend on how incomplete observations are classified or addressed.

The analysis populations are not reported in the registry record. The stated enrollment is 145, while the adverse-event denominators are 49 for the Bipolar Ablation group and 60 for the Patient Registry group. The record does not explain the relationship between these counts, enrollment, eligibility, or outcome-specific analysis sets. It also does not report participant flow, exclusions, withdrawals, or the number with complete primary endpoint follow-up. Those omissions prevent a full assessment of who contributed to each outcome.

Interim analyses and stopping rules are not reported in the registry record. The absence of these details in the record should not be interpreted as evidence that such procedures did or did not occur.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: recurrent ventricular tachycardia (18.4%), pericardial effusion (12.2%), cardiac tamponade (8.2%), pulmonary embolism pneumonia (6.1%), congestive heart failure (5.0%).

The registry lists serious adverse events and other adverse events separately for the Bipolar Ablation and Patient Registry groups. For serious adverse events, 26 of 49 participants are listed in the Bipolar Ablation group and 25 of 60 in the Patient Registry group. For other adverse events, the corresponding figures are 14 of 49 and 8 of 60. Deaths are listed as 9 and 5, respectively. These are descriptive counts, not a randomized comparison or an estimate of causal effect.

The record does not explain whether a participant could appear in both the serious and other adverse-event categories, whether counts represent people or episodes in every listing, or how long participants were followed for these safety summaries. It also does not specify whether deaths are included within another event category. The figures should therefore be kept in their posted categories rather than added or treated as mutually exclusive.

The registry additionally lists serious-event terms and percentages: Recurrent Ventricular Tachycardia, 18.4%; Pericardial Effusion, 12.2%; Cardiac Tamponade, 8.2%; Pulmonary Embolism Pneumonia, 6.1%; Congestive Heart Failure, 5.0%; and Hemorrhagic Shock, 4.1%. The denominators and group-specific meaning of these percentages are not reported in the registry record. They should not be interpreted as rates for either group or compared with the participant counts without that context.

General statistical principle: safety figures describe what was recorded under particular definitions and observation conditions. They do not by themselves establish whether an event was caused by an intervention. The non-randomized design and unequal clinical pathways are further reasons to avoid causal interpretation.

13. What the Result Does, and Does Not, Mean

The registry record describes a study of bipolar ablation in participants with VT not terminable by unipolar ablation and a patient registry group following successful unipolar ablation. It defines freedom from recurrent VT at 6 months as the primary endpoint and posts several adverse-event counts. These registry entries establish the intended clinical question and some descriptive safety information; they do not establish the primary endpoint outcome.

The primary endpoint count and its uncertainty are not reported in the registry record. Therefore, the posted information does not show how many participants achieved freedom from recurrence or how precisely that outcome was estimated. The stated hypothesis about arrhythmia termination and complication risk must not be read as a result. Likewise, the existence of secondary outcomes in the registry does not indicate what their findings were.

The serious and other adverse-event counts can be reported as recorded, but they do not demonstrate that an intervention caused or prevented an event. Death counts are also listed, but the record does not describe their causes or relation to treatment. The percentages attached to the listed serious-event terms have no reported denominator or group-specific context in the posted information, limiting interpretation.

The groups are not exchangeable by design: one is described in the setting of unipolar ablation failure, while the registry group follows unipolar success. Without randomization or a reported analysis addressing group differences, outcome contrasts would not isolate the effect of bipolar ablation. Even a numerical difference, if available, would require cautious interpretation and consideration of confounding and uncertainty.

General statistical principle: evidence about an outcome is strongest when the endpoint is clearly defined, the analysis population and missing-data approach are transparent, and estimates are accompanied by suitable measures of uncertainty. Here, important outcome and analysis details are not reported in the registry record. The posted data support a limited description of study design and adverse-event listings, not a definitive efficacy or comparative-safety conclusion. No medical decision should be inferred from these registry entries alone.

14. Why This Trial Matters Statistically

This study raises a useful statistical question about how to interpret evidence from a treatment pathway in which eligibility and group membership are linked to the success of prior treatment. The bipolar group consisted of participants whose VT was not terminable with unipolar ablation, while the patient registry group followed successful unipolar ablation. Because those groups enter the comparison with different treatment histories, a raw contrast would mix the effect of the procedure under study with differences that may have preceded it.

That issue is not resolved simply by labeling one group an intervention and the other a comparator. In a non-randomized study, the comparison is observational unless a design or analysis supports stronger causal interpretation. The record explicitly notes that the arms are not a like-for-like control comparison. This makes careful separation of descriptive results from causal claims particularly important.

The endpoint also illustrates why a clear outcome definition is necessary but not sufficient. The registry specifies a 6-month period and a recurrence definition based on sustained VT lasting longer than 30 seconds, identified through symptoms or device interrogation. Yet the result, analysis population, follow-up completeness, and uncertainty are not reported. Without them, readers cannot assess either the observed frequency of the endpoint or the precision of an estimate.

The safety listings similarly show the difference between describing counts and estimating comparative risk. Group denominators accompany several participant counts, but other details—including event overlap, follow-up duration, and the context for the serious-event percentages—are not reported. These omissions constrain comparisons and causal interpretation.

More broadly, a registry record can identify prespecified outcomes and study structure, but it may not contain the detail needed to evaluate every statistical question. Sample-size justification, interim analyses, multiplicity handling, missing-data methods, and analysis populations are not reported. Recognizing those limits is part of sound biostatistical reading: the design and data that are posted can be described without treating missing information as a finding.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The central limitation for interpreting outcomes is that the registry record does not report the primary endpoint result. It gives the definition of freedom from recurrent VT at 6 months but not the number achieving it, the number with recurrence, or an uncertainty estimate. Consequently, the main outcome cannot be quantitatively assessed from the posted record.

The non-randomized design also limits comparative interpretation. The bipolar group is described as including participants whose VT was not terminable with unipolar ablation, whereas the Patient Registry group followed successful unipolar ablation. The groups therefore differ by prior treatment outcome and are not a like-for-like control comparison. No adjusted comparative analysis is reported in the registry record.

There is an unexplained difference between listed enrollment of 145 and adverse-event denominators of 49 and 60. The record does not describe participant flow, eligibility exclusions, reasons for missing observations, or how these denominators relate to the primary outcome population. Analysis populations and endpoint follow-up completeness are not reported.

Several details needed for safety interpretation are also absent. The record does not explain event overlap, observation duration for the safety counts, or the group-specific denominators underlying the listed serious-event percentages. It does not provide event timing or attribution for the posted counts. These omissions prevent a detailed comparison or causal interpretation.

The registry record does not report sample-size justification, a statistical analysis plan, multiplicity handling, missing-data methods, or interim analyses. It lists zero analyses. These gaps limit assessment of whether outcomes were analyzed as intended and how uncertainty or multiple endpoints were handled. They should be understood as information not reported in the registry record, rather than evidence that any particular method was or was not used.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Bipolar Ventricular Tachycardia (VT) Study — NCT02374476.
• Registry record last updated 2022-11-01; status last verified 2022-10.
• Results first posted 2022-11-01.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

The registry describes a completed, non-randomized, parallel-model study of bipolar ablation for refractory scar-related ventricular arrhythmia. Enrollment is listed as 145, masking as none, and phase as NA. The listed start date is 2015-02-18 and the primary completion date is 2020-04-01.

The primary outcome is the number of participants achieving freedom from recurrent VT at 6 months, defined using sustained VT lasting longer than 30 seconds and identified through clinical symptoms or device interrogation. The primary result is not reported in the registry record.

Posted adverse-event figures list serious events, other events, and deaths for the Bipolar Ablation and Patient Registry groups. The record cautions that this is not a like-for-like control comparison. It lists six outcome measures and zero analyses. Sample-size justification, primary endpoint analysis details, missing-data methods, and analysis populations are not reported in the registry record.